Short answer
A presumptive screen tells you whether residue is above a threshold; a laboratory sample tells you how much is there, in µg/100cm². Screen first to find out whether there is anything to investigate, then use laboratory samples where you need a figure for a negotiation, an insurer, a tribunal or a clearance.
Side by side
| Presumptive screen | Laboratory wipe sample | |
|---|---|---|
| Result | Above or below a threshold | Measured µg/100cm² |
| Method | Swab and reagent, read on site | NIOSH 9111 wipe, chain of custody, laboratory analysis |
| Speed | On the day | Depends on laboratory turnaround |
| Best for | Finding out if there is anything to investigate | Negotiations, insurance, tribunals, clearance |
| Coverage per dollar | High | Lower |
How a screen works
A screen uses a swab over a marked area and a reagent that changes when methylamphetamine is present above the kit’s threshold. The code of practice notes 0.5 µg is the maximum reporting level for screening kits, provided the sample covers 100cm². Screens are fast and inexpensive, which is why they suit whole-property coverage.
How a laboratory sample works
The NIOSH 9111 method uses a 10 × 10 cm template, a gauze wipe pre-wetted with methanol, three passes in different directions, and a sealed, labelled sample sent with a chain-of-custody record. The code calls for a NATA- or IANZ-accredited laboratory, and at least one blank per property so the laboratory can show the media was not contaminated.
Discrete and composite
A discrete sample is one surface, one result. A composite combines several wipes into one analysis to save cost, and gives up knowing which surface contributed. Composite results average across locations, so a single high surface can be diluted; ask how a composite has been assessed before relying on it.
Using both
For most homes the efficient plan is:
- Screen every room, plus garage and any second dwelling.
- Send laboratory samples from any room that screens positive.
- Use laboratory samples again for clearance after any works.
Questions
Are meth screening kits accurate?
They indicate presence above a threshold. The Environmental Health Australia code notes 0.5 µg is the maximum reporting level for screening kits when sampled over 100cm². They do not give a measured concentration.
Can a screen be used for clearance?
Queensland Health advises that samples taken after works be tested by an accredited laboratory that can certify the result, so clearance uses laboratory analysis.
Is laboratory testing always better?
It is more precise, but costs more per sample. Screening every room and sending only positives to the laboratory gives most properties the best coverage for the cost.
Sources
- Australian Voluntary Code of Practice: Assessment, remediation and validation — former clandestine drug laboratories and other methamphetamine contaminated properties (2019) — Environmental Health Australia
- Illicit drug laboratories — Queensland Health
- Clandestine Drug Laboratory Remediation Guidelines (2011) — Australian Government — Attorney-General’s Department / Australian Crime Commission
Facts on this page checked against these sources on 29 October 2026.